Magnetically self-returning ball armature relays



Nov. 4, 1958 F. D. REYNOLDS 2,359,297

MAGNETICALLY SELF-RETURNING BALL ARMATURE RELAYS Filed 001:. 28, 1954 2 Sheets-Sheet 1 IN VEN TOR. FBAUC/S D. REY/VOL D5 fl ifwdmqm A 7' TOQJUEYJ Nov. 4, 1958 Y F. D. REYNOLDS 2,859,297

' MAGNETICALLY SELF-RETURNING BALL ARMATURE RELAYS Filed Oct. 28. 1954 2 Sheets-Sheet 2 /4 zea 24 Z0 mmvrox I FR/M/C/S O. REYUOLOJ BY .44., Mdm

A T702. MEYS 'MAGNETICALLY SELF-RETURNING BALL ARMATURE RELAYS Francis D. Reynolds, Seattle, Wash., assignor to Boeing Airplane Company, Seattle, Wash., a corporation of Delaware Application October 28, 1954, Serial No. 465,259

11 Claims. (Cl. 200-87) essentials thereof may be incorporated in various modified forms without departing from the inventive concepts.

Electromagnetically actuated relays of the self-returning type following conventional or previously known designs have certain inherent limitations and disadvantages which are largely overcome by the present invention.

Such shortcomings in most cases result from the use of spring-returned or gravity-returned armatures and associated features of relay construction incident thereto. Many if not all such relays are not inherently or basically suited to meet the growing requirement for fast-acting relays of increasingly smallerphysical size and weight with adequate load current capacity and minimum actuating current requirements, long and reliable operating life expectancy, consistency of operation in any physical attitude, and the capability of attaining and holding any given switching position under shock and vibration. All of these requirements are becoming increasingly important in the developing art of electrical controls and functional electronic apparatus.

"The present invention directs itself generally to the provision of a novel type of relay basically and uniquely capable of meeting the above-mentioned objectives and 7 others as will hereinafter more fully appear.

In brief outline the present invention utilizes a single electrically conductive ferromagnetic sphere or ball as the sole physically movable electrical switching element operatively associated with a set or plurality of sets of switch contacts in the relay. Referred to hereinafter as the relay armature ball, such element is held captive within an air gap common to and defined between magnetic pole face-switch contact surfaces in the combined permanent magnet system and electromagnetic system of the relay. Within such air gap the armature ball is free to move between alternate switching positions bridging between ditferent sets of magnetic pole faces adapted as the switch contacts. Normally the armature ball is held by permanent magnetic flux in engagement with one set of pole face-switch contacts. By energization of the relay coil the ball is instantly attracted into engagement with an alternate set of contacts, representing the actuated position, where it remains until deenergization of the coil, whereupon the temporarily established magnetic flux collapses and the permanent magnetic flux instantly returns the ball to the normal position.

It has been found that the physical size and mass of such a relay switching element may be reduced to a very small order of magnitude, such as of the order of a millimeter diameter with all the attendant advantages of smallness of size and lightness of weight, and still present a relatively low contact resistance when interengaged with pairs of switch contact surfaces under the force of magnetic attraction. Moreover, the amount of magnetic flux re- United States Patent til quired to establish firm physical contact hence low-resistance electrical contact and, of equal importance for many applications, to maintain such contact against the dislodging forces of shock or vibration, is small relative to that required to achieve a similar result with other, former types of relay armatures. Short actuation time and small energization requirements are further advantages of such a relay. Moreover, the reliable operating life expectancy of such a device is virtually limitless because of the absence of any flexible parts subject to crystallization, or of parts which become defective due to uneven wear. By properly encapsulating the relay device or that portion incorporating the armature ball and associated contacts to eliminate dust and moisture therefrom, reliably consistent contact resistance is achieved throughout repeated actuations, despite the small size of the ball.

These and other features, objects and advantages of the invention will become more fully evident from the following description thereof by reference to the accompanying drawings.

Figure 1 is a simplified largely schematic view of a basic form of relay incorporating the invention.

Figure 2 is a similar view of a modified form incorporating two armature balls and associated groups of relay contacts.

Figure 3 is a simplified perspective view of a second modification in which two armature balls and associated groups of contacts are incorporated.

Figure 4 is a simplified largely schematic view of a 1third modification, and Figure 5 is a slight variation of the atter.

Figures 6 and 7 illustrate a detail of construction based on the form of the device shown in Figure 1, Figure 7 being a sectional view taken on line 77 in Figure 6.

Referring to Figure 1, the electrically conductive ferromagnetic armature ball 10 is received in the air gap 12 defined by and between mutually adjacent pole faces of permanent magnet means comprising the U-shaped permanent magnet 14 and electromagnet means comprising the ferromagnetic core structure element 16, likewise of U shape, and the associated ferromagnetic element 18 serially arranged therewith in a continuous magnetic flux path including the air gap 12. Both of the ferromagnetic elements 16 and 18 are of low retentivity material. The element 18 serves also as a part of the permanent magnet means, namely as a keeper for the U-shaped permanent magnet 14. The upper pole faces of the ferromagnetic element 16 andthe permanent magnet element 14 are disposed in substantially parallel relationship on opposite sides of the air gap 12, whereas the upper pole face of the ferromagnetic element 18 is disposed on the lower side of such air gap, substantially perpendicular to the first-mentioned pole faces. The air gap 12 is common to the permanent magnet system and the electromagnet system of the relay. The lower portion of the ferromagnetic element 19 .lies directly between the lower pole faces of the ferromagnetic element 16 and the permanent magnet element 14, with short air gaps separating the element 18 from the other two for purposes of electrical insulation. The upper end portion of the element 18 is also separated slightly from the upper end portions of the elements 14 and 16 for reasons of electrical insulation and also in order to minimize the demagnetization eifect on the permanent magnet element 14 accompanying the establishment of temporary magnetic flux in the magnetic path comprising the serially arranged elements 16 and 18. Such magnetization is effected by means of the relay coil 20 wound on the element 18 and having energization terminals 20a and 20b.

As will appear from the figure, each of the elements 14, 16 and 18 is provided with an electrical connection enabling such element, or more specifically the electrically conductive pole face thereof associated with the armature ball 10, to function as a switch contact in the relay device. Thus the ferromagnetic element 16 is elec trically connected to a relay terminal 22 by means of a conductor 22a. Similarly, the element 18 is electrically connected to the terminal 24 by means of conductor 24a, and the element 14 to the terminal 26 by means of the conductor 26a.

Any suitable means (not shown) may be employed for rigidly supporting each of the elements 14, 16 and 18 and the coil 20 in fixed relation to the other elements, and for housing the apparatus as well as providing means for'mounting the same in any desired apparatus. Likewise, it will be recognized that, especially in the case of subminiature relay applications, wherein the relay device is very small it is preferred to encapsulate or enclose the "device or at least the ball armature and associated magnetic pole faces as switch contacts in order to eliminate dust and moisture as well as any gases or other chemicals which might impair the electrical contact established between the small armature ball and the sets of pole -face-electrical contacts. These details are not shown in the drawings since they may vary widely with preference or design requirements and are not essential to an understanding of the nature and operation of the invention.

In Figure 1 the ball armature is shown in its normal position simultaneously engaging the upper pole face of permanent magnet element 14 and that of ferromagnetic element 18. Thus an electrical circuit is closed between relay terminals 24 and 26. Such position of the ball is, of course, established by the passage of permanent magnet flux serially through the U-shaped permanent magnet element 14, the ferromagnetic element 18 and the air gap 12in which the ball 10 is captive. With readily attainable magnetic flux densities established in the air gap 12, hence through the ball armature 10, a relatively large holding force is exerted on the ball armature, maintaining low-resistance electrical contact between the spherical surface of the ball and the substantially fiat electrically conductive pole face surfaces of the magnet 14 and element 18.

By "energization of relay coil with a polarity productive of temporary magnetic flux in the path comprising the U-shaped ferromagnetic element 16, the element 18, and the air gap 12, in a sense in which the upper or ball-contacted pole face of element 18 becomes of like magnetic polarity to the adjoining pole of permanent magnet '14, namely a south pole in the example, the armature ball is immediately attracted away from the permanent magnet pole and into simultaneous contact with the adjacent upper poles of elements 16 and 18. This represents the actuated position of the armature ball, in which a closed circuit is formed between relay terminals M nd 24. Upon removal of energization from coil 20 the temporary magnetic fiux established serially in the elements 16 and I8 collapses and the armature ball is immediately attracted back into its normal position by the force of the permanent magnet flux.

It will be evident from the foregoing description of the operation of the device shown in Figure 1 that positioning and actuation of the armature ball 10 depends entirely on magnetic forces and takes place quite independently-of physical attitude of the device, although for convenience in the description the apparatus has been described with'a certain orientation. It is found that in a miniature form of such a device, wherein the armature ball has a diameter of the order of one or a few millimeters, it is easily possible to create magnetic holding forces in either position of the ball, that is, by permanentmagnet flux or by temporary electromagnet flux, which are sufiicient to hold the ball in either of its alternate' positions against very considerable shock and vibration forces involving acceleration effects in any direction. Thesrnall physical size and mass of the ball, and its. configuration as a factor in establishing the flux pattern through the air gap 12 provides this result. Moreover, the spherical configuration of the ball bearing against the cooperating magnet pole face surfaces provides a condition in which the two requirements for low contact electrical resistance are satisfied, namely finite contact surface area yet great contact pressure. Obviously, such a device possesses a virtually limitless life of trouble-free operation since there are no moving parts which can wear in a manner influencing the operation of the relay. Any wear of the spherical armature ball 10 or of the cooperating pole faces of the magnetic elements will be largely distributed wear and even should such wear be somewhat localized in particular areas, as on the pole face surfaces, it will have negligible effect upon the operating characteristics of the device. For most applications it is preferred that the armature ball, being basically of ferromagnetic material, be plated over its entire surface with a low resistance metal such as copper, silver or aluminum, the cooperating pole face surfaces engaged by the ball and serving as relay switch contact surfaces likewise being similarly plated.

Referring to the modified form appearing in Figure 2, the same basic principles of construction and operation employed in Figure 1 are utilized in achieving the equivalentof a double-pole, double-throw relay. In this case two separate relay armature balls 28 and 30 are employed, similar to the ball 10 in the preceding form. The ball 28 is received in an air gap 32 defined by and between the associated upper pole faces of permanent magnet and electromagnet elements, whereas the ball 30 is similarly received in the air gap 34 defined by and between the associated lower pole faces of cooperating permanent magnet and electromagnet elements. The permanent magnet 36 is U-shaped, having upper and lower parts 36a and 36b, respectively, arranged in additivepolarity serial relationship with a short air gap therebetween for electrical insulation purposes. Similarly, the ferromagnetic U-shaped element 38 is formed with upper and lower parts 38a and 38b separated by a short air gap, the same being true of the intermediate ferromagnetic element 40, having upper and lower. parts 40a and 40b, as shown. A single relay coil means 42 is wound on the mutually aligned parts of the ferromagnetic element 40 and has energizing terminals 40a and 40]). Both the elements 40 and 38 are of low-retentivity ferromagnetic material as in the preceding form. Upper relay switch terminals 44, 46 and 48 are respectively connected to the upper magnet element parts 36a, 40a and 38a, respectively. Similar relay switch terminals 50, 52 and 54 are connected to the magnet elements 38b, 40b and 36b, respectively.

In the absence of energization of the relay coil means 42 by application of voltage to terminals 40a and 40b permanent magnet flux is established by permanent magnet element 36 in the serially arranged air gaps 32 and 34 and in the aligned upper and lower segments 40a and 40b of the keeper element 40. Thus in the normal position of the relay armature balls 28 and 30 as shown, electrical circuits are closed between contacts 44 and 46 and between contacts 52 and 54. However, upon energization of coil 42 establishing temporary magnetic flux in the magnetic circuit comprising the serially arranged elements 40a, 40b, 34, 38b, 38a and 32, and with a polarity of ferromagnetic element 40 corresponding to the polarity of the permanent magnet, the armature balls are immediately attracted by this temporary magnetic fiux into actuated positions closing electrical circuits between sets of contacts 46 and 48, and and 52, respectively.

In the second modification shown in Figure 3, likewise a double-pole, double-throw form of relay, the two armature balls 56 and 58 are received in air gaps disposed in side-by-side or parallel magnetic path relationship as opposed to the series arrangement of Figure 2. In effect,

the arrangement shown in Figure 3 involves a pairing of the single pole relay form shown in Figure 1. Thus, the two similar U-shaped permanent magnets 60 and 62,

placed in side-by-side parallel relationship can be made similar to the permanent magnet 14 in the first described embodiment, the two similar ferromagnetic elements 64 and 66, likewise disposed in parallel side-by-side relationship can be made similar in form and disposition to the ferromagnetic element 16 in the first described embodiment, and the two elements 68 and 70 also similar both in form and disposition to the corresponding element 18 in the first embodiment. However, a single relay coil 72 wrapped around both of the elements 68 and 70 provides the necessary magnetizing force for both temporary magnetic flux paths comprising the elements 64 and 66 respectively. Relay switch terminals 74, 76 and 78 are respectively connected to the magnet elements 60, 68 and 64, whereas relay switch terminals 80, 82 and 84 are similarly connected to elements 62, 70 and 66, respectively.

In Figure 3, as in Figure 2, in the absence of energizing voltage applied to the terminals 72a and 72b of coil 72, the armature balls 56 and 58 are magnetically held in simultaneous contact with the upper pole faces of permanent magnet elements 60 and 62 and the cooperating ferromagnetic keeper elements 68 and 70, respectively. Energization of such coil efiects reversal of the position of the balls during the period of energization.

In Figure 4 the basic principles ofthe magnetically self-returning ball armature relay are incorporated in a modified construction wherein the ferromagnetic element 16 of Figure 1 is replaced by the permanent magnet element 86, and the upper pole face of this element and the opposite-polarity upper pole face of a similar permanent magnet element 88 are formed and relatively disposed to define an air gap 90 therebetween loosely receiving the armature ball 92. A ferromagnetic bar element 94, comprising two parallel parts 94a and 94b placed side by side and electrically insulated from each other, has its lower end portion received between the lower magnetic poles of the permanent magnets 86 and 88, but electrically insulated therefrom. The upper end portions of the bar elements 94a and 9412 together form a magnetic pole face defining the lower boundary of the air gap 90. The upper pole faces of magnets 86 and 88 are inclined so as to diverge downwardly from each other, whereas the upper end portions of the two bar elements 94a and 94b are inclined so as to diverge upwardly from each other. Thus the armature ball 92 is receivable in either of three corners formed by mutually adjacent pole faces, that bea tween the permanent magnet upper ends and those, at right and left, between such ends and the adjacent bar member upper ends.

A relay coil 96 is wound on the ferromagnetic element 94 and has energizing terminals 96a and 96b. In the absence of energization of this coil the permanent magnet flux which flows serially through the permanent magnets 86 and 88 and through the air gap 90 and the ball 92 received therein holds the ball in an upper, normal position bridging directly between the upper pole faces of these permanent magnets and out of contact with the bar elements 94a and 94b. The relay contact terminals 98 and 100 are electrically interconnected in this position of the ball 92. Upon energization of the coil 96 with a polarity such that the upper ends of the bar elements 94a and 94b assume a polarity like that of the upper pole of permanent magnet 88, namely a north pole in the example, the armature ball 92 is both repelled and attracted into a position simultaneously engaging the upper pole face of permanent magnet 86 and the right-hand bar element 94a, since there is then a predominant concentration of magnetic flux in the circuit comprising the permanent magnet 86. In this position of the armature ball the relay output terminals 98 and 102 are interconnected. When the polarity of energization of coil 96 is reversed relative to that producing the immediately foregoing result, the armature ball 92 is immediately attracted into the left-hand position simultaneously engaging the upper pole face of permanent magnet 88 and the upper pole face of bar element 94b. This encloses an electrical circuit between relay terminals 100 and 104.

When the coil 96 is deenergized the temporary flux collapses and the ball 92 is immediately attracted to its normal position bridging directly between the upper pole faces of the two permanent magnet faces 86 and 88.

It will therefore be seen that the modified relay device shown in Figure 4 is a triple-throw type switching device in which any one of three sets of electrical contacts are interconnected by the ball armature depending upon the condition of energization of the relay coil, namely whether it is deenergized or whether it is energized with one polarity or with the opposite polarity, respectively.

The revised apparatus shown in Figure 5 is in all respects similar to that shown in Figure 4, with the exception that the permanent magnet elements 88 and 86 have been electrically interconnected and provided with a common relay output terminal 106, so that in this instance the relay device becomes in effect a singlepole, double-throw switching device having a normal open circuit condition, i. e. with the ball 92 interconnecting none of the relay output terminals, and positionally controlled for switch actuation in accordance with the polarity of energization applied to the relay coil 96. If desired terminals 102 and 104 may also be interconnected with the result that the relay will be non-polarized.

The illustration presented in Figures 6 and 7 is of a basic magnetically self-returning relay device in all respects similar to that shown in Figure 1 except for the formation of the upper pole face of the ferromagnetic element 18'. Like elements are assigned similar reference numerals to those used in the first-mentioned form. In this case the upper pole face of the element 19 is channeled or V-shaped with downwardly convergent surface portions 18'a and 18'b (Figure 7) forming a ball guide trough extending perpendicularly to the mutually parallel upper pole faces of the permanent magnet elements 14 and 16. The armature ball 10 in traveling between the latter two pole faces in accordance with energization or deenergization of the coil 20 is thereby caused to roll on a track and has two points of contact on the pole face surfaces supporting it. This dual point contact of the ball provides increased magnetic holding force on the ball in either extreme position and increases the surface area of electrical contact thereof with the element 18, hence lowers the electrical contact resistance thereof. Moreover, such pole face construction tends to stabilize the ball positionally within the air gap 12.

These and the variations employing the described features of the invention will be apparent to those skilled in the art.

I claim as my invention:

1.. Electromechanical relay apparatus comprising a ferromagnetic core structure including serially arranged ferromagnetic elements defining a magnetic flux path of low magnetic retentivity, two of said elements having mutually adjacent end portions spaced apart to form an air gap interposed in said magnetic flux path, a single electrically conductive ferromagnetic relay armature ball loosely received in said air gap, permanent magnet means disposed adjacent said ferromagnetic core structure and having an end portion constituting a permanent magnetic pole positioned immediately adjacent one of said element end portions and passing permanent magnetic flux through said air gap and said latter element as a keeper for said permanent magnet, and thereby normally attracting said armature ball magnetically into normal. position directly contacting said permanent magnet end portion and said keeper element end portion simultaneously but displaced thereby out of contact with the other of said element end portions, and relay coil means inductively linked with said core structure and energizable for establishing magnetic flux in said flux path, hence through said air gap between said mutually adjacent end portions for attracting said armature ball into relayactuated position directly contacting said two mutually adjacent element end portions simultaneously but displaced out of contact with said permanent magnetic end portion, at least two of said three end portions having electrically conductive surfaces contacted by said armature ball and being provided with relay switch terminal connections adapted for connecting the same in an electric circuit opened and closed by magnetically controlled positioning of said armature ball.

2. Electromechanical relay means comprising an electromagnet including a ferromagnetic structure of relatively low magnetic retentivity and including a relay coil on said core structure, energizable to pass magnetic flux L therethrough, said core structure having electromagnet 'pole faces separated to form an opening therebetween traversed by such magnetic flux, a single electrically conductive ferromagnetic relay armature ball loosely received in said opening between said pole faces, said electromagnet pole faces being disposed relatively at an angle and respectively having mutually adjacent electrically conductive surfaces thereon simultaneously contactable by said armature ball by magnetic attraction during energization of said relay coil, permanent magnet means having magnetic poles and positioned relative to said ferromagnetic structure with one of said permanent magnetic poles disposed immediately adjacent said opening to pass ball-attracting magnetic flux therethrough from a location relative to said electromagnet pole faces to attract said ball out of contact with the electrically conductive surface of at least one of said latter pole faces during deenergization of said relay coil, and electric circuit connecting means electrically connected to said electromagnet pole face conductive surfaces.

3. Electromechanical relay means comprising an electromagnet including a ferromagnetic structure of relatively low magnetic retentivity and including a relay coil on said core structure, energizable to pass magnetic flux therethrough, said core structure having electromagnet pole faces separated to form an opening therebetween traversed by such magnetic flux, a single electrically'conductive ferromagnetic relay armature ball loosely received in said opening between said pole faces, said electromagnet pole faces being disposed relatively at an ant gle and respectively having mutually adjacent electrical- 1y conductive surfaces thereon simultaneously contactable by said armature ball by magnetic attraction during energization of said relay coil, permanent magnet means having magnetic poles and positioned relative to said ferromagnetic structure with one of said permanent magnetic poles having an electrically conductive surface disposed immediately adjacent said opening to pass ballattracting magnetic flux therethrough from a location relative to said electromagnet pole faces to attract said ball out of contact with the electrically conductive surface of one of said latter pole faces and into simultaneous contact with the other of said electromagnet surfaces and said permanent magnet pole face surface during deenergization of said relay coil, said other electromagnet pole face surface and said permanent magnet pole face surface being disposed relatively at any angle and at a relative spacing permitting of such simultaneous ball contact therewith, and electric circuit connecting means electrically connected to the last-mentioned electromagnet pole face conductive surface and at least one of the remaining two said pole face conductive surfaces.

4. The relay means defined in claim 3, wherein the electromagnet ferromagnetic structure comprises serially arranged ferromagnetic elements having respectively mutually adjacent and relatively substantially perpendicular end faces constituting the electromagnet pole face surfaces, and wherein the permanent magnet pole face surface is disposed substantially perpendicular to one of said end faces and parallel to the other of said end faces, said permanent magnet being disposed relative to the ferromagnetic structure to pass permanent magnet flux serially through the ball receiving opening and that ferromagnetic element having its end face disposed perpendicular to said permanent magnet pole face surface.

5. The relay mean's defined in claim 4, wherein the mutually parallel electromagnet pole face surface and permanent magnet pole face surface are disposed adjacent relatively opposite sides of the other electromagnet pole face surface, and the latter surface has inwardly convergent bottom portions simultaneously contacted by the armature ball to roll on such bottom portions between alternate positions of contact respectively with said mutually parallel pole face surfaces.

6. Electromechanical relay apparatus comprising permanent magnet means, an electromagnet ferromagnetic element of relatively low magnetic retentivity, said element having an electrically conductive pole face, said permanent magnet means having an electrically conductive permanent magnet pole face disposed adjacent and at an angle to said ferromagnetic element pole face to form an air gap therebetween, a single electrically conductive ferromagnetic armature ball loosely received in said air gap and magnetically attractable into simultaneous contact with said pole faces, another ferromagnetic element having an electrically conductive pole face disposed adjacent and at an angle to one of said first-mentioned two pole faces, adjoining said air gap, electromagnet coil means inductively linked with said first-mentioned ferromagnetic element and energizable to pass magnetic flux through said latter element and thereby through said air gap, and through said second-mentioned ferromagnetic element to attract and hold said armature ball in simultaneous contact with said pole faces of said two ferromagnetic elements solely by and during energization of said coil means, and electric circuit connection means electrically connected to said first-mentioned ferromagnetic element pole face and at least one of said other pole faces.

7. Electromechanical relay apparatus comprising permanent magnet means, electromagnet means including a ferromagnetic element of low magnetic retentivity and an electromagnet coil means operatively associated therewith, said permanent magnet means and electromagnet means ferromagnetic element each having a set of electrically conductive pole faces adapted and connected as electrical switch contacts and defining an open air gap common to all of said pole faces situated in respectively different sides of said air gap, and a single electrically conductive ferromagnetic relay armature ball received in said air gap and magnetically actuatable between alternate positions of simultaneous engagement with different pole faces in accordance with the relative concentration of magnetic flux passing through said air gap between the pole faces of the respective sets, said arma ture ball being returned and held in one such position of contact engagement by the permanent magnetic flux of said permanent magnet means in the absence of coil means energization, and being attracted and held in a different such position of engagement solely by and during energization of said coil means.

8. The relay apparatus defined in claim 7, wherein the permanent magnet means includes a pair of permanent magn'et pole faces of relatively opposite polarity constituting one set of switch contacts engaged by the armature ball absent energization of the coil means, and wherein the electromagnet means ferromagnetic element includes a pole face cooperatively disposed relative to 9 see of said permanent magnet pole faces for simultaneous engagement of the armature ball therewith upon energization of the coil means making the polarity of said ferromagnetic element pole face opposite the polarity of said cooperating permanent magnet pole face.

9. The relay apparatus defined in claim 7, wherein the permanent magnet means includes a pair of permanent magnet pole faces of relatively opposite polarity constituting one set of switch contacts engaged by the armature ball absent energization of the coil means, and wherein the electromagnet means ferromagnetic element in'cludes a pole face having separate portions electrically insulated from each other and respectively cooperatively disposed relative to both of said permanent magnet pole faces for simultaneous engagement of the armature ball alternatively with one or the other such portions and the respectively associated permanent magnet pole face, upon energization of the coil means with one polan'ty or the other respectively.

10. The relay apparatus defined in claim 7, wherein the electromagnet means ferromagnetic element has two serially arranged portions having mutually adjacent end portions comprising one set of switch contact pole faces adjoining the air gap, one of said latter pole faces cooperating with a pole face of the permanent magnet means to form a second set of switch contact pole faces, the armature ball being normally held in engagement with the latter set by permanent magnet flux but being actuatable into engagement with the former set by energization of the coil means.

11. Electromechanical relay apparatus comprising permanent magnet means having magnetic pole face elements forming physically spaced, relatively inclined surfaces, a single electrically conductive ferromagnetic ball received in the space between said surfaces and normally attracted into simultaneous contact with said surfaces by the permanent magnet flux, electromagnet means including ferromagnetic means defining a magnetic flux path for said electromagnetic means and having pole face means presenting at least one surface adjoining said space and disposed relative to said permanent magnet pole face elements to attract said ball out of simultaneous contact with said first-mentioned surfaces and into contact with said last mentioned surface upon establishment of magnetic flux above a predetermined value, in said electromagnet flux path, and coil means operatively associated with said ferromagnetic means and energizable to establish such balls attracting flux, at least two of said surfaces being electrically conductive, and electrical switch connections for said conductive surfaces, said permanent magnet means having residual magnetic flux sufficient to attract said ball back into contact with said first-mentioned surfaces upon deenergization of said coil means.

References Cited in the file of this patent UNITED STATES PATENTS 684,378 Potter Oct. 8, 1901 685,549 Wurts Oct. 29, 1901 2,253,856 Harrison Aug. 26, 1941 2,732,454 Buckingham Jan. 24, 1956 2,732,458 Buckingham Jan. 24, 1956 

